Los Angeles is a seasonable southern city on the west coast. Its average monthly maximum temperatures are historically confined to the 64-77 ºF range year round [source]. Unsurprisingly, the big concern for residents in terms of energy efficiency is the cost of air conditioning. One of the major sources of heat entering the house is through window light. So southern Californians, like residents of other longitudinally southern U.S. states, have taken to applying reflective windows treatments, both as a cost-saving measure and as a "green" energy saver.

But in this case the approach backfired, as the neighbors' energy efficient reflective gloss created a brilliant beam during daytime hours that directed itself directly at the car port.

"The side view mirrors were melting. Anything that was plastic on the car was melting," the Prius-owner recalls.

And Ms. Patron says her Prius wasn't the only ones damaged -- a neighboring vehicle saw similar melting. She comments, "I'm positive that this window is what is causing the damage to my car. I just don't feel like it’s fair. I feel like it needs to be known that this is happening. And a lot of people probably have damage out there, that they aren't aware that it’s the windows that are causing this."

She claims to have measured the temperature in the car port when it's exposed to the beam and found it to be 120 ºF.

Similar claims of reflective windows burning people or plastics were leveled in Sept. 2010 by a lawyer staying at the Vdara hotel in Las Vegas, Nevada. Reportedly in that case the situation was even more severe as the reflective windows were acting as a hyperbolic solar dish, focusing sunlight into a "death ray", which swept across the pool deck.

Reportedly other homeowners have also complained about plastic-melting reflective beams coming off windows with certain energy-efficient treatments. The National Association of Home Builders has promised a thorough investigation into this problem.

What makes Ms. Patron's story more curious is that automotive mirror housings are usually primarily composed of ABS (acrylonitrile butadiene styrene) [source] -- the same type of plastic found in LEGO blocks and plastic pipes. Pure ABS has a melting point of 221 ºF [source], so it's unclear how the beam was able to melt the plastic, even if the air temperature was 120 ºF.

One possibility was that the black mirror plastic absorbed the light, and heated up to a temperature far hotter than the surrounding air (think of an Easy-Bake oven).

The Prius is the best-selling hybrid electric vehicle in the U.S. (and in the world).
[Image Source: Jason Mick/DailyTech]

I'm guessing if the owners aren't faking this, then any black plastic ABS car mirror would see similar melting. Toyota's mirrors aren't exactly special to my knowledge.

I would say the video (see the source link) tends to support their claims as it shows small dimples as melting first. Typically molded plastics have pockets of poorly set plastic -- structural weak points. If exposed to a large amount of heat, theses would go first, hence the dimpled look.

Would it help if Toyota applied a glossier finish? Say silver? Sure. But the victim's car (and its mirrors) were black.

At the end of the day, the key problem here IS the windows, if the results are confirmed. After all, do you really want your neighbors melting your kids' sandbox and toy trucks? Are you going to blame Tonka for "poor quality" in that they didn't protect their plastics against an intense solar beam?

And you can be sure that if you have a lawn and/or backyard garden/landscaping, a 120 F beam will do a pretty good job cooking them. Is it the plants fault for not being designed well enough?

The current incident showcases the problem nicely as its the worst case scenario -- a black plastic. This makes it the perfect color to absorb the majority of the visible and near-visible spectrum. Anyone who's run outside on a sunny day in a black T-shirt knows this. Basic physics.

From what I understand there are alternative gloss treatments that reflect a more diffuse, scattered light.

Precisely on pointTo the original OP... abs plastic has been used to cast a majority of automotive plastics from bumpers to mirrors to window trims or antenna flashing for 20+ years. The same abs plastic mirror having the "issue" is likely no different in composition than cars nearing antique status. This does present a quite unique situation though. Maybe it would be wise in hotter regions to enact ordinances on special reflective treatments that have a scatter pattern (diffusing the light). Otherwise yea, it's like lining your house with mirrors.

A state or neighborhood ordinance for something like this is entirely acceptable and, frankly, preferred. States rights, look it up. What in the hell does that have to do with Obama or the "government"?

Actually this would preferably be kept between the parties involved and keep even the local gov't out if possible. It should be my right to reflex light wherever I want and for whatever reason if it doesn't hurt anyone else. What if there was a solar panel where the car was? That would be a good reason to do it.

Do we need an ordinance for excessive <insert problem here>? No. You can call the cops to help with your neighbors even if there isn't a law. And if it elevates higher than that we have a court system.

And if that fails, set up a mirror to reflect the same light at their car ;-)

The open carport receives enough radiant heat to raise the air from 77 to 120 degrees? Peak solar about 1kw per meter sq. So 1KW direct from sun and assume 1kw for reflection. With 120 degree ambient. So at what point does the black body mirror housing obtain convective heat balance with the incident radiation of 2kw/meter? Yep about 200C, good melting point for most PVC'shttp://www.engineeringtoolbox.com/convective-heat-...

Yep the 2KW / meter sq. is general, but is the rate that a surface receives heat, regardless of the surface area (assuming no lens or focusing effect). This basically cancels area out of this, "back of the envelope" type "is it possible," calculation. Area cancels because convective heat transfer (cooling) very proportional to surface area, as is heating (the area exposed to the radiation (light)).

The interesting thing here is that the damage is outside of the car. There doesn't appear to be any internal damage too, which is what one would expect.Looking at the video, it appears another car which also uses the same car port also has the same damage; and it also appears the light is focused and not an even spread, which would point to either a manufacturing defect in the window concerned or the way the reflective coating was applied caused the window to become slightly concave.As a thought, if the thermal expansion and contraction of the reflective coating was significantly different from that of glass, then it could cause the window to focus light under the right conditions. E.g. if the coating was internally applied and the thermal expansion of the coating was greater, then when the window and the coating are warmer than when the coating was originally applied then the reflective coating would actually "suck" on the window causing it to focus sunlight.

quote: The interesting thing here is that the damage is outside of the car. There doesn't appear to be any internal damage too, which is what one would expect.

I was thinking about this. Conclusion is that glass transmits UV radiation very well but transmits IR radiation poorly. In direct sun your interior heats up because the UV heats the components inside the vehicle which then radiate off IR radiation as heat which does not get transmitted back through the glass and causes the interior temperature of a vehicle to rise far above the outside air temperature. If the coating on the building is reflecting more IR than UV then it is going to heat up the outside of the vehicle more than the inside since the glass on the vehicle will not transmit it.

I don't believe it is 100% the window. In fact, I would be surprised if the window was at fault at all.

You can tell from the video that the reflected light is rather dispersed by the time it hits the ground, and since the window is not concave the light would not have passed its focal point so the mirror would have received even less light.There is no other direct light hitting the car because the car port is covered, so the only source of light is from the relatively small window.The window is transparent, so not all of the suns light is being reflected as some will continue through the glass.The melting on the other car was at a strange angle compared to the window (which is located on a wall above it). I would have expected the melt to have covered the whole area exposed to the glass, not just a small stretch of it.

While I do agree that the mirror damage looks heat related, the window does not look like the source.

You just contradicted yourself. If in Phoenix it gets to 120F and cars don't have a problem even when uncovered (I'm sure people in Phoenix have Priuses) then that supports the idea the glare from the windows was the cause, by focusing reflected heat on the black plastic casing and greatly heating it above air temperature. Also notice, her car was in a car port, and thus "covered".

Additionally, this also happened to another neighbor's car, but I didn't see where that type of car is listed. Still, that increases our sample size. And we have previous reports of similar things.

It really isn't a surprise: heat has to go somewhere, and if you aren't letting it in, but reflecting it tightly, it's going to go right where you're directing it. Remember, you can't destroy energy.

The real danger is a fire starting; especially in the dryer summer months if one of these reflected heat beams gets focused on dry grass. How would they fix this? Just make the reflective coating of these heat mirror windows simply disburse the light rather than gather and reflect.

Problem comes in the shape of the window/windows. If they total surface reflecting is concave then it will focus the sunlight, if it was convex then it would disperse it. If you have a four window set on that side of the building say in a two by two arrangement and it happens that the corners of those windows which are nearest the center of the grid all are recessed into the building slightly then you have a concave mirror which would focus the light reflecting from them, if those same corners are protruding from the building slightly then you would have a convex mirror and the sunlight would not be concentrated into a smaller area.

Seems here there is just the right combination of window shapes, direction the house is oriented and relative position of the neighboring carport to cause some serious problems.

Not an easy fix. Probably double pane windows sealed with argon or nitrogen in between. How much they flex and what shape they take depends on atmospheric pressure and temperature of the gas (and how much it expands or contracts relative to outside air). They are sealed TIGHT to prevent moisture from getting inside as well.

I agree that this is not Toyota's fault. If they made high temperature plastics you know what happens? They become brittle when temperatures are low. And if you put softer plastics that are more flexible in lower temperatures without shattering, they melt in the Phoneix sun.

Here's a fun fact that applies more for a circular piece of glass but should be similar for a square: if a 48" glass flat is ground to a saggita (depth of arc) of 1/8", it would have a focal point about 100' away. It wouldn't be a perfect focus for a couple reasons, but you could get a lot of light concentrated into a very small area even with a fairly small curvature. The plate glass would probably never distort by 1/8", but I could a lot of energy being dumped into a black mirror.